Felted fibrous web or batt

ABSTRACT

A FELTED FIBROUS WEB OR BATT HAVING ENCHANCED RESILIENCY IS PRODUCED WITH FROM 10% TO 100% SHORT FIBERS OF CHEMICALLY PULPED WOOD. A RESIN BINDER IS USED WHICH INCLUDES A CELLULOSE REACTIVE CROSSLINKING REAGENT.

O. R. VIDEEN ET AL May 4, '1971 FELTED FIBnous WEB on BATT Fuera Feb. 21, 196e 50- l 24 ll 22 1 /NvE/vroRs: l I

,1' ons R. v/DEEN "VM Aw 30 A B C 0 DONA D .E W/EGA/VD RESINE/vcr REs/L/EA/cr cme 20 crass THE/f? arromvgr C OMPE SS VE RESISTANCE CYCLE COMPRESS/VE HES/SMNCE 20 C YC L E S Patented May 4, 1971 3,577,312 FELTED FIBROUS WEB OR BATT Otis R. Videen, St. Paul, and Donald E. Wiegand, Minneapolis, Minn., assignors to Conwed Corporation, St. Paul, Minn.

Filed Feb. 21, 1968, Ser. No. 707,147 Int. Cl. D21h 5/12 U.S. Cl. 162--148 10 Claims ABSTRACT F THE DISCLOSURE A felted fibrous web or batt having enhanced resiliency is produced with from to 100% short fibers of chemically pulped wood. A resin binder is used which includes a cellulose reactive crosslinking reagent.

Felted fibrous webs of many kinds are known and are used for a variety of purposes, including upholstery padding, mattress padding and filling, other cushioning and padding applications, and thermal insulation.

The functional characteristics of the various webs or blankets known vary according to a number of variables, including the vtype ,and length of fiber, the binders used, and the method of production. It has long been understood, for example, that longer fibers such as the textile fibers (both synthetic and natural) generally produce Webs having kappreciably better resiliency when compressed than do similar webs made from shorter fibers such as the more common wood fibers and still much shorter chemically pulped wood fibers. Indeed, the chemically pulped wood fibers are generally so short, being about 1.5 mm. in length, that they are practically dust.

Accordingly, when it is important in the application for which the ultimate web or blanket is to be used that the resiliency be maximized, then, in that event, such short fibers are avoided, despite their generally lower cost.

One example of a web incorporating longer fibers and exhibiting enhanced resiliency is disclosed in U.S. Pat. No. 3,181,225 issued to N. B. Knoepfier et al. In that patent, combinations of cotton fibers and first-cut cotton linters are utilized, together with a particular resin binder, to produce webs or blankets having excellent resiliency.

Generally, however, products having the longer fibers display lower compressive resistance and, when used in p cushioning, tend to bottom-out so that the feel of the Vsubstructure passes through to the surface, thus permitting the substructure (such as springs) to be felt by those sitting on the cushioned product. It is known that short fibers such as the more common wood fibers and the still much shorter chemically pulped wood fibers generally improve the compressive resistance. Such short fibers, however, also decrease resiliency as indicated above.

Applicants have found, surprisingly, that when very short fibers of chemically pulped wood are incorporated in batts, mats or webs having binders as used in the above mentioned U.S. Pat.A No. 3,181,225, either alone or in combination with longer fibers, there is an unexpected increase in resiliency over products rnade only with the long fibers, while, at the same time, obtaining the advantage of shorter fibers in an increase of compressive resistance.

' These and other advantages will be evident to those skilled in the art from the following description and drawings in which:

FIG. 1 shows one type of apparatus for producing felted webs; and

FIG. 2 is a graph of different property values of various webs.

" Various methods and apparatus are known for producing fibrous webs, including conventional garnett devices, and various apparatus for producing felted webs from air suspensions of fibers. One such device for producing webs or blankets from air suspensions of fibers is disclosed in U.S. Pat. No. 3,010,161 issued to T. C. Duvall.

Said U.S. Pat. No. 3,010,161 discloses an apparatus similar to that shown in FIG 1. Such apparatus includes a chamber 50 positioned over a continuously moving conveyor 52. At one end of the chamber 50 there is provided a duct 54, connected to a disperser mechanism 56 of the hammermill type. The disperser 56 provides an air 4suspension of short fibers in the duct 54. Between the disperser 56 and the chamber 50, the duct 54- is restricted at the point 58, where there is arranged a picker-roll 60 which serves to feed fibers (generally of the longer variety such as cotton fibers) from a supply `62 into the stream of short fibers existing within the duct 54. The air stream having shorter fibers therein doffs the longer fibers from the teeth of the picker-roll 60y and produces an air suspension 64 containing both shorter fibers and longer fibers, all as described in said Pat. No. 3,010,161. Adjacent the outlet of the duct 54 are spray nozzles 66 which serve to spray liquid binder particles into the stream 64 to provide binder on the fibers as they settle upon the screen 52 forming the mat 70. The conveyor then conveys the mat 70 under suitable compression rolls 72 and into a dryer mechanism 74.

As indicated above, conventional garnett mechanisms may be utilized to felt the web and may be provided with suitable spray nozzles for applying the binder as indicated in the above mentioned U.S. Pat. No. 3,181,225. It is, however, generally difiicult to handle the very short fibers of chemically pulped wood on such garnett machines. Other conventional apparatus used in the production of non-woven textiles may also be used.

By any of the methods and apparatus referred to above, suitable felted fibrous webs with applied binder may be produced, which are then subsequently dried if necessary and heated to activate the binder. It is known to incorporate in such fibrous webs a resin binder formed from a composition in which at least one of the components is a cellulose reactive crosslinking reagent which not only reacts with the other component to form a resin but also reacts with the cellulose of the cotton fibers. Such binders include binders of which one component is ureaformaldehyde and the other component is a vinyl acetate copoly mer. Other such resin binders may be formed from compositions of which one component is a methylated methylol melamine and the other component is a vinyl acrylic copolymer. While a binder is preferred that is formed from a composition of which one component is an imidazole and the other is a vinyl acrylic copolymer, still other compositions will serve, such as one in which one component is dimethylol ethyl carbamate and the other component is any one of a number of latices such as a vinyl acrylic copolymer, a styrene-butadiene copolymer, a vinyl acetate polymer, or mixtures thereof. As indicated, such binders used with cotton fibers to form a web or blanket have been previously disclosed in Pat. No. 3,181,- 225.

Applicants have discovered that unexpected advantageous results are achieved by incorporating in fibrous mats having such cellulose reactive resin binders a quantity of chemically pulped wood fibers in amounts of from 10% to of the total weight of fiber with the remaining fiber, if any, being cotton fibers. 'Such chemically pulped wood fibers are very short, generally being in the range of about 1.5 mm. to 2.0 mm. It was to be expected that when 10% or over of the total fiber weight comprised such short fibers of chemically pulped wood the mat would show an increased compressive resistance and a lowered resiliency. Generally, quantities of such short fibers below 10% (based upon the total ber weight) would not be [particularly noticeable in the properties of the mat, since their presence would be masked by the binder and other bers present.

Surprisingly, however, applicants have discovered that when 10% or more of such chemically pulped wood bers are incorporated in mats utilizing resin binders of which one component is a cellulose reactive crosslinking reagent, such mats unexpectedly improve in resiliency and, at the same time, demonstrate an increase in compressive resistance.

In each of the following examples the products made were tested for four product characteristics, as follows:

The compressive resistance after one cycle was determined by stacking 6 x 6" samples to a height of about 3" and then accurately measuring the height of the stack. The stack was then compressed between two flat metal plates of 6" x 6" or larger at a rate of 2 per minute to 1/3 of its original measured height. The amount of pressure to compress the stack was measured in pounds and converted to pounds per square foot.

The resiliency after one cycle is expressed in percent and was determined by immediately removing the load from the stack after it had been compressed to 1A; its height (in determining the compressive resistance after one cycle) and permitting the recovery of the stack for 45 seconds. After that time, the height of the stack was again measured and the resiliency after one cycle was determined n percent by dividing the recovered height by the original free height and multiplying by 100.

The compressive resistance after 20 cycles was determined by repeating the compression and release cycle 20 times and measuring the pressure in pounds required on the 20th cycle to compress the stack to 1/a its original measured height and converting such pressure in pounds to pounds per square foot.

The resiliency expressed in percent after 20 cycles was determined by removing the load from the stack immediately after the 2()th compression and permitting the stack to recover for 45 seconds. Again, the height was measured and divided by the original free height of the stack and multiplied by 100.

In the tables set forth hereinafter and in PIG. 2 of the drawings, the letter A represents the compressive resistance for the rst cycle, the letter B represents the compessive resistance for the 20th cycle, the letter C represents the resiliency after the first cycle, and the letter D represents the resiliency after the 20th cycle.

EXAMPLE I A commercially available product was obtained which had been made in accordance with U.S. Pat. No. 3,181,- 225, from cotton textile waste bers and including some irst-cut kcotton linters. The product contained 20% |by weight of the product as binder solids, which binder was a two-component binder, one component of which was an imidazole resin and the other component of which was a self-reacting vinyl acrylic latex. The product was found to have a density of 2.3 pounds per cubic foot and a thickness of 0.702. The product was tested for the properties A, B, C, and D and the results are tabulated in Table I below and plotted in line l of FIG. 2. The numerals in the third column of Table I are the reference numerals in FIG. 2.

4 EXAMPLE n A fibrous web was formed on apparatus such as that shown in FIG. 1 by felting from an air suspension of fibers a mat or web containing 30% (by weight of the total fibers) of cotton .fibers obtained from cotton textile Waste such as picker or ily. The mat also incorporated 70% (by weight of the total fibers) of chemically pulped wood iibers pulped by the sulphite process. The shorter iibers of chemically pulped wood bers were introduced from a disperser such as shown at 56 in `FIG. 1, and the longer cotton -bers were introduced with the picker-roll 60. The binder was sprayed by means of the nozzles 66 into the depositing fiber mixture in an amount to provide 20% by Weight of the final product as binder solids. The mat was then heated in oven 74 to dry the mat and activate the binder. 'If-he binder used was a twocomponent binder comprising an imidazole resin as one component and a self-reacting vinyl acrylic latex as the other component. The inal product was found to have a density of 2.26 pounds per cubic foot and a thickness of 0.873. The product Was tested for the four product properties A, B, C, and D. The results are tabulated in Table II below and plotted graphically in line 20 of FIG. 2.

A brous web was formed by felting in the same manner as |Example II by felting from an air suspension of iibers. The web or mat formed contained 100% (by weight of the total bers) of chemically pulped Wood libers pulped by the sulphite process. Since there were no long fibers used in this example, it was not necessary to use the feeding mechanism 60 shown in FIG. 1 and the `fibers could be dispersed directly into the chamber 50. The binder applied by the nozzles 66 Was the same binder as applied in Example I'I above and was added in a quantity to provide 20% by weight of the iinal product as binder solids. The mat was then heated in oven 74 to dry the mat and activate the binder. The product was found to have a density of 2.7 pounds per cubic foot and a thickness of 0.64 The product was tested for the product properties A, B, C, and D. The results are tabulated in Table III below and plotted graphically in line 30 of FIG. 2.

EXAMPLE IV A iibrous web was formed on conventional textile equipment commonly used for non-woven fabrics. A mixture of (by weight of the total bers) of cotton waste Iiibers and 15% (by Weight of the total bers) of chemically pulped wood fibers pulped by the sulphite process was rst preblended with a precarder of conventional type. The mixture was then fed to a picker-roll from which it was doled into an air stream. The air suspension of bers was then felted onto a. condensing roll to provide a thin web. The web was hand sprayed with binder and laid up in laps to provide the nal product thickness. The lapped product was then heated in an oven to dry the mat and activate the binder. The binder used was a two component system of which one cornponent was a. methylated methylol melamine and the other component was a self-reacting vinyl acrylic latex. Binder was provided in an amou-nt to supply 12% of the final product Weight as binder solids. The final product was found to have a density of 2.5 pounds per cubic foot and a thickness ofY 0.423". The product was tested for the properties A and C. The results are tabulated in Table IV below and plotted in FIG. 2 as points 42 and 46. The product properties B and D were not determined.

vTABLE 1V Figure 2 reference Property value numeral Property:

A 438 pounds/square foot- 42 C 92.9% 46 It will be seen from reviewing the data given above in Tables I, II, and III, and by viewing the lines 10, 20, and 30 in FIG. 2, that in all instances the very short fibers of chemically pulped Wood gave increased compressive resistance to the product as compared with products having only the longer cotton fibers. This is clearly illustrated for the properties A and B, in which the product of Example II illustrated in line 20 shows a significant increaes in compressive resistance when 70% by weight of the total fibers are chemically pulped wood fibers as compared with the product of Example I illustrated in line in which product there were no such fibers. In the product of Example III illustrated in line 30, where all of the fibers are chemically pulped wood fibers, the compressive resistance is still further increased. The product of Example IV, in which only of the fibers were chemically pulped wood fibers, also shows an increase in compressive resistance (property A) at 42 in FIG. 2 over the product of Example I (see point 12), in which there were no such fibers. The degree of increase in compressive resistance was not as great for the product of Example IV as for the products of 4Examples II and III, in which greater amounts of such short chemically pulped wood fibers were used. This increase in compressive resistance l(properties A and B) was to be expected, but not in the degree of increase demonstrated above.

Of even more significance is the improvement in resiliency (properties C and D) demonstrated by the products of Examples II, III, and IV. In the product of Example IV, in which there were only 15 of chemically pulped Wood fibers, the resiliency of 92.9% for the property C (see point 46 in FIG. 2) is a significant improvement in resiliency over the value 89.2% for the product of Example I (see point 16 in FIG. 2). The significance in this improvement is not in its amount but in the fact that there was any improvement at all, in view of the inclusion in the mat of the very short fibers of chemically pulped wood. Indeed, the product of Example IV demonstrated this improvement despite the fact that this product had a somewhat lesser usage of binder than the product of Example I. When the products of Examples II and III (having 70% and 100%, respectively, of the very short fibers of chemically pulped wood) are considered, the improvement in resiliency is remarkable. The values for resiliency of 94.1%, 88.6%, 95.2%, and 91.2% (points 26, 28, 36, and 38, respectively) are very significantly above the values of 89.2% and 79.2% (points 16 and 18, respectively) for the resiliency values demonstrated by the product of Example I. No such increase was to be expected with the addition of the extremely short chemically pulped wood fibers, and certainly no such increase was to be expected when all of the fibers were chemically pulped wood fibers. Indeed, a decrease in resiliency (properties C and D) was expected. Short fibers, and particularly the very short fibers of chemically pulped wood, are not considered to be as spring-like as longer fibers such as the cotton waste fibers used in Example I. In fact, such 'short fibers are considered by many authorities to be equivalent to dust and, as such, to act more like granular particlesthan likelfibers.

It is not known, nor need it be known, exactly why the addition of short fibers to mats of this type having a resin binder of which one component is a cellulose reactive cross-linking reagent should have the-unexpected effect of improving the resiliency of the mat, contrary to previously known characteristics of such short fibers. The above mentionedUS. Pat. No. 3,181,225 indicates that such resins react with the cellulose molecules of the cotton fibers lby crosslinking or other phenomenon to enhance the resiliency of the fibers. Since these chemically pulped wood fibers also have a cellulose component, it would be expected that such resins would improve their resiliency also; however, this does not explain why such resins should improve the resiliency of such short chemically pulped wood fibers way beyond the improvement that such resins give to the longer, inherently more resilient cellulose cotton fibers. As one possible explanation, it is hypothesized that the cellulose of the chemically pulped wood fibers is different from the cellulose of the cotton fibers and that a different or additional chemical reaction takes place that is 'not understood or known. In this regard, it should be pointed out that the improvement in resiliency, both for one cycle and for 20 cycles (properties C and D, respectively), of the mats containing the short chemically pulped wood fibers (Examples II, III, and IV) over the resiliency of the mat of Example I is very significant. Resiliency values in the range of 88 to 95% have not previously been achieved, so far as applicants are aware, for fibrous webs or mats.

We claim:

1. In a product comprising a batt of felted cellulosecontaining fibers, said batt including a resin binder formed from a composition at least one component of which is a cellulose reactive crosslinking reagent, said reagent having been reacted with the cellulose of` said fibers and with at least one other component of said binder, said batt being of a density suitable for cushioning material in furniture having a 1 cycle resiliency of at least about 90%, the improvement comprising from 10% to 100% by weight of said cellulose-containing fibers being chemically pulped wood fibers, whereby the compressive resistance of said batt is enhanced.

2. The product of claim 1 in which said batt has a 20 cycle resiliency of at least about 80%.

3. The product of claim 2 in which said batt has a l cycle compressive resistance of at least about 400 pounds per square foot.

4. A product comprising a batt of felted cellulosecontaining fibers, said batt being bound by a binder, said binder including a resin, said resin being formed from a composition one component of which is a cellulose reactive crosslinking reagent, said batt being of a density suitable for cushioning material in furniture, said cellulose-containing fibers including cotton fibers in an amount of from 10% to 90% by weight of the total cellulosecontaining fibers, said cellulose-containing fibers also including chemically pulped wood fibers in an amount of from 10% to 100% by weight of the total cellulose-containing fibers, and said batt having a 1 cycle resiliency of at least about 90%.

5. The product of claim 4 in which said batt has a l cycle compressive resistance of at least about 400 pounds per square foot.

6. The product of claim 4 in which said batt has a 20 cycle resiliency of at least about 7. The product of claim 6 in which said batt has a 1 cycle compressive resistance of at least about 400 pounds per square foot.

8. In a product comprising a batt of felted cellulosecontaining fibers, said 'batt including a resin binder formed from a composition at least one component of which is a cellulose reactive crosslinking reagent, said reagent having been reacted with thecellulose of said fibers and. with at least one other component of said binder, said batt being of a density suitable for the cushioning material in furniture having a 1 cycle resiliency of at least about 90%, said cellulose-containing bers including cotton fibers in an amount of from 0% to 90% by weight of the total cellulose-containing fibers, the irnprovement comprising from 10% to 100% by weight of said cellulose-containing fibers being chemically pulped Wood fibers, whereby the compressive resistance of said batt is enhanced.

9. The product of claim 8 in which said batt has a 20 cycle resiliency of at least about 80% 10. The product of claim v9 in which said batt has a References Cited UNITED STATES PATENTS 10 HOWARD R. CAINE, Primary Examiner T. G. SCAVONE, Assistant Examiner U.S. C1. X.R.

1 cycle compressive resistance of at least about 400 15 117-140, 145; ll-170; 162-149, 164; 264-121 pounds per square foot. 

